An off-road vehicle may be defined as a road vehicle having some off road capability—such as the provision of all wheel drive. Off road vehicles are often required to travel through water to reach their intended destination. Travel through deep water (typically over about 0.3 m in depth) is known as “wading”. Known off-road vehicles are design to wade, and comprise suitably sealed closures to avoid ingress of water into the passenger compartment. The engine air intake is positioned at an elevated position (normally directly in front of and below the windscreen) to prevent water being ingested into the engine, and this intake will often dictate the maximum level of water relative to the body that the vehicle can wade through.
Prior art methods of determining if the water level is safe to wade through include referring to depth gauges, e.g. permanent graduated poles situated within the water in the case of fords and measurement of the depth by the driver using a partially submerged stick or pole.
As discussed, the maximum wading depth is determined by the position of a point on the vehicle body (e.g. the engine air intake). Because the ride height of the vehicle is often variable (due to the variable height of the suspension system) the permissible absolute depth of water which the vehicle can wade through varies depending on the selected ride height of the suspension system.
The behaviour of the water around a wading vehicle is influenced by the vehicle's speed. The driver will typically want to travel as fast as possible (to reach a destination) but high speed travel whilst wading is not advisable. Waves from the vehicle may damage surrounding structures (and lap over e.g. flood defences) and excessive speed may cause waves to lap over the vehicle itself, entering e.g. the engine air intake. Evidently the maximum speed at which the wading vehicle can travel whilst avoiding these effects depends on factors such as water depth and pitch of the ground surface, but unless the driver is highly experienced in wading there is a significant risk that the maximum speed may be exceeded for a given set of wading conditions. Very low speed wading may be indicated in urban environments to avoid damage due to the vehicle's wash.
An aim of the present invention is to at least mitigate the above mentioned problems by providing better information to the driver.